running an air conditioner on 250 feet of cord

In my experience, the 15 amp outlet slowly drops voltage. After about 10 minutes it's typically lower than I would be comfy with. maybe I could have dropped more stuff out of the circuit before hand though. If I were you, I would consider a hard start capacitor, running the fan on low, and even consider the fan delay circuit that smkettner shared here a couple years ago.